"We don't really know why this happens, but we do know it's an allergic reaction," Rhoads said. "It's diagnosed by endoscopy and biopsy. One way to treat it is to eliminate the most allergenic foods. The two most likely culprits are wheat and milk."

Rhoads said kids with this condition typically have trouble swallowing and begin losing weight.

"Some of the older kids will say it feels like food is getting stuck," Rhoads said. "If you have a child that wants to drink but not swallow food, this is something that needs to be considered."

Milk allergies affect 3 percent to 4 percent of the general population, but the very term "allergy" is often misused said Dr. Dat Tran, a pediatric allergist at Children's Memorial Hermann Hospital and assistant professor of pediatrics at University of Texas Health Science Center.

More Information

Allergy or intolerance?

Allergy

A Most common culprits involve casein and whey

A Symptoms typically involve gut, skin and respiratory reactions

A 3-4 percent of the general population has a milk allergy, which most often surfaces in infancy

A Most outgrow the allergy by age 5

Intolerance

A Involves lactose, a naturally-occurring sugar in dairy products

A Symptoms are typically limited to the gut

A Lactose intolerance affects some 30 million Americans, and tends to surface in adulthood

A Can be temporary as the result of a stomach virus

A true allergy, Tran said, happens when the immune system rebels against something it perceives to be a foreign or harmful substance. This results in the release of histamines and leukotrienes, leading to symptoms of itchiness, swelling and redness. In some cases, an eczemalike rash appears as well as asthmalike symptoms and tummy troubles. In severe cases, it can lead to a life-threatening anaphylactic reaction.

Tran said the dairy allergens that most often cause a reaction are casein and whey.

An allergic reaction will present itself within 30 minutes of exposure to the allergen, Tran said, but it also needs to happen more than once. First exposure to the allergen is basically an educational phase, he said, during which the body is digesting what's going on and isn't sure yet how to react. That's why most babies aren't diagnosed until around 3 months of age, Tran said.

It's not uncommon for people to think a milk allergy is present when what's really going on is lactose intolerance. Lactose, Tran said, is a natural sugar found in dairy products. If an individual is short on lactase, the enzyme responsible for breaking down lactose, unpleasant symptoms prevail.

"The lactose accumulates in the gut and acts like a sponge," Tran said. "It starts to pull water from the intestines, causing diarrhea - which can happen pretty fast."

Lactose intolerance is much more prevalent than milk allergies, but sometimes it takes a gastrointestinal physician to get to the bottom of what's going on.

Rhoads said only about 5 percent to 10 percent of tummy-distressed kids coming through his clinic are actually suffering from a milk allergy. In those cases, the most common symptom Rhoads sees is rectal bleeding, even in breast-fed babies.

"She was doing well until she was about one month old," said Ana Sofia's mother, Ana Maria Orozco. "First she showed some symptoms of eczema on her face, and later, when I was changing her diaper, there were some streaks of blood in her bowel movements. It irritated her bottom so bad, you cannot imagine. She was miserable. We didn't know what to do."

Orozco was breast feeding, so she eliminated all dairy from her diet, but it didn't help. Eventually the baby was diagnosed with a milk allergy. Rhoads said 90 percent of infants with a milk allergy do well on special formulas created specifically for this reason.

It took five tries to find the right product for Ana Sofia, but today the 7-month-old is thriving - and she will likely outgrow her milk allergy. About 75 percent outgrow it by the first or second year of life, and 90 percent by 5 years of age.

"My advice to parents is to be a good observer," said Orozco, Ana Sofia's mother. "Understand how serious food allergies can be."